Colour picture tubes

ABSTRACT

In a colour picture tube comprising a colour selecting member provided with a plurality of stripe shaped parallel perforations extending in the direction of vertical or horizontal deflection, a fluorescent screen including a plurality of stripe shaped phosphors corresponding to the stripe shaped perforations, and an electron gun, each stripe shaped perforation is divided into a plurality of slit shaped sections by means of spaced apart lateral bridges and the height of the bridges is made smaller than the thickness of the colour selecting member so that adjacent sections are separated by the bridges on the side facing to the electron gun assembly whereas they merge with each other on the side facing to the fluorescent screen.

Yamada et al.

[ COLOUR PICTURE TUBES [75] Inventors: Junichi Yamada; Etuzo Terashima,

both of Mobara-City, Japan [73] Assignee: Hitachi, Ltd., Tokyo, Japan[22] Filed: Jan. 4, 1973 [21] Appl. No.: 321,019

[30] Foreign Application Priority Data Jan. 19, 1972 Japan 47-008061[52] US. Cl. 313/403 [51] Int. Cl. H01j 29/06 [58] Field of Search313/85 S, 403, 408

[56] References Cited UNITED STATES PATENTS 2,690,518 9/1954 Fyler et al313/408 3,663,854 5/1972 Tsuneta et al 313/85 S 3,666,462 5/1972 Kaplan313/85 S 3,760,214 9/1973 Yamasaki et a1. 313/858 [451 May 13,1975

Primary Examiner-Ronald L. Wibert Assistant ExaminerRichard A.Rosenberger Attorney, Agent, or FirmDike, Bronstein, Roberts, Cushmanand Pfund [57] ABSTRACT In a colour picture tube comprising a colourselecting member provided with a plurality of stripe shaped parallelperforations extending in the direction of vertical or horizontaldeflection, a fluorescent screen including a plurality of stripe shapedphosphors corresponding to the stripe shaped perforations, and anelectron gun, each stripe shaped perforation is divided into a pluralityof slit shaped sections by means of spaced apart lateral bridges and theheight of the bridges is made smaller than the thickness of the colourselecting member so that adjacent sections are separated by the bridgeson the side facing to the electron gun assembly whereas they merge witheach other on the side facing to the fluorescent screen.

10 Claims, 5 Drawing Figures PATENTED HAY I 3 I975 SHEET 2 OF 2 COLOURPICTURE TUBES BACKGROUND OF THE INVENTION This invention relates to acolour picture tube, more particularly to a colour picture tubeutilizing a colour selecting member or electrode provided with aplurality of stripe shaped perforations.

With a widespread use of colour television receivers in recent years,various types of colour picture tubes have been developed including thecolour picture tube utilizing a colour selecting member or electrode(called hereinafter a colour selecting member) having a plurality ofstripe shaped perforations described above. Since the colour picturetube of this type does not require any adjustment of the electron beamor electron gun in one direction, typically in the vertical direction,it is possible to produce pictures of higher colour purity than thecolour picture tube utilizing a shadow mask of well known constructionwith a more simple electronic circuit. In this type of the colourpicture tube, however, as a plurality of stripe shaped perforations areformed in the colour selecting member to extend substantially the entirevertical or horizontal width thereof, the colour selecting member tendsto vibrate in response to mechanical shocks or large audio volume raisedby a speaker incorporated in a colour television receiver during theoperation of the colour picture tube.

According to one approach developed for solving these problems, finemetal wires, for example steel wires, are provided across the stripeshaped perforations, the wires being spaced apart in the longitudinaldirection of the perforations. However, as it is necessary to secure thesteel wires to the colour selecting member by means of spot welding forexample, the stripe shaped perforations divided with said steel wiresare deformed so that this method can not be applied to a sphericalcolour selecting member.

According to another approach, bridges which are suitably spaced apartin the longitudinal direction of the stripe shaped perforations of thecolour selecting member are provided to traverse the perforations whichare extending in the direction of the vertical deflection forreinforcing the colour selecting member, as disclosed in thespecifications of a I-Iaan et al US. Pat. No. 3,186,884 dated June I,1965 (US. patent application Ser. No. 126360, filed May 2, 1960). Whenphotosensitive material coated on the inner surface of the face plate ofa colour picture tube is exposed to light transmitting through a colourselecting member of this construction to form stripe shaped phosphors,the portions of the photosensitive material corresponding to the bridgesare not sufficiently exposed thereby causing uneven exposure whichdecreases the quality of the reproduced picture. Moreover, the electronbeam emanated from an electron gun is reflected by the side walls of thebridges to cause halation.

SUMMARY OF THE INVENTION It is an object of this invention to provide animproved colour picture tube which does not require any adjustment ofthe picture in the vertical or horizontal direction and yet can producestable pictures of high colour purities.

Another object of this invention is to provide a new and improved colourpicture tube provided with stripe shaped phosphors on the inner side ofthe face plate which are continuous between the opposite ends andwherein the halation caused by the electron beam is minimized.

A further object of this invention is to provide an improved colourselecting electrode which has sufficiently large mechanical strength andcan form uniform and continuous stripes of phosphors on the fluorescentscreen of a colour picture tube.

In accordance with this invention, there is provided a colour picturetube comprising a colour selecting member provided with a plurality ofstripe shaped parallel perforations extending in a direction parallel toone side of the picture displayed by the tube, each stripe shapedperforation being divided into a plurality of slit shaped sections bymeans of spaced apart bridges extending in a direction perpendicular tothe first mentioned direction, a fluorescent screen including aplurality of stripe shaped phosphors corresponding to the stripe shapedperforations, and an electron gun assembly, characterized in that theheight of the bridges is made smaller than the thickness of the colourselecting member so that adjacent sections are separated by the bridgeon the side facing to the electron gun assembly whereas they merge witheach other on the side facing to the fluorescent screen.

BRIEF DESCRIPTION OF THE DRAWINGS This invention can be more fullyunderstood from the following detailed description taken in conjunctionwith the accompanying drawings in which:

FIG. 1 is an enlarged plan view ofa portion of one example of a colourselecting member utilized in the colour picture tube of this invention;

FIG. 2 is an enlarged plan view ofa portion ofa modified colourselecting member utilized in the colour picture tube of this invention;

FIG. 3 shows a cross section of the colour selecting member shown inFIG. 1 taken along a line III-III;

FIG. 4 shows a cross section of the colour selecting member shown inFIG. 1 taken along a line lV-IV; and

FIG. 5 shows a sectional view corresponding to FIG. 3 of anothermodification of the colour selecting member.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIGS. 1, 3 and4 of the accompanying drawing, the colour selecting member 1 showntherein comprises a plurality of spaced apart parallel rows of stripeshaped perforations 2, each being divided by transverse bridges 3 into aplurality of slit shaped sections 2a. The bridges 3 in each stripeshaped perforation 2 are spaced apart in the longitudinal direction ofthe perforation. As shown in FIG. 3, the height of each bridge 3 issmaller than the thickness of the colour selecting member 1 so that theopening 2b of each section 2a facing toward the electron gun assembly issmaller than the opening 2c on the side facing the fluorescent screen.In other words, adjacent openings 2c merge with each other to form asingle opening. The height of each bridge may be equal to or smaller orlarger than one half of the thickness of the colour selecting member.Such bridges of reduced height can be prepared by etching such that theportions of the bridges 3 facing to the fluorescent screen are removedcompletely, whereas the portions of the bridges on the side facing tothe electron gun assembly are not etched.

For this reason, when the photosensitive material coated on the innersurface of the face plate is exposed to light transmitting through thestripe shaped perforations 2, portions of the photosensitive materialcorresponding to the bridges are also irradiated sufficiently becausethe exposure light 4 transmits obliquely through respective sections 2aof the stripe shaped perforations 2 as shown in FIG. 3. This advantageis provided by the decreased height and tapered construction of thebridges. The height of the bridges is determined by taking intoconsideration the degree of reinforcement of the colour selecting memberand the degree of removal of the halation.

In one example, a steel sheet having a thickness of about 0.15 mm wasetched from the side of the fluorescent screen to form stripe shapedperforations at a pitch of 0.6 mm with bridges spaced apart 1 mm. Thewidth of the sections of the stripe shaped perforations was 0.14 mm onthe side facing to the electron gun assembly and 0.3 mm on the sidefacing to the fluorescent screen, and the width of the bridges was 0.05mm on the side facing to the electron gun assembly. The height of thebridges was 0.06 mm.

Although in the embodiment described above, the bridges of respectivestripe shaped perforations were aligned in the horizontal direction, inthe modification shown in FIG. 2, the bridges 3 are not aligned in thehorizontal direction but staggered. This arrangement of the bridgesincreases the mechanical strength of the colour selecting member beyondthat of the first embodiment.

As shown in FIG. 5, the bridges may protrude slightly beyond the surfaceof the colour selecting member on the side thereof facing to theelectron gun assembly.

Although in the foregoing embodiments, the stripe shaped perforationswere shown as extending in the direction of vertical deflection it willbe clear that the perforations may extend in the direction of horizontaldeflection.

As above described, with the colour selecting member of this inventionit is possible not only to form continuous and uniform stripes ofphosphors on the inner surface of the colour picture tube but also todecrease the halation caused by the electron beam reflected by the sidewalls of the bridges. Moreover, as it is possible to increase theresistance of the colour selecting member against mechanical shocks andvibrations the colour picture tube can reproduce stably pictures of highcolour purities.

What is claimed is:

1. In a color picture tube comprising a colour selecting member providedwith a plurality of stripe shaped parallel perforations extending in adirection parallel to one side of the picture displayed by said tube,each stripe shaped perforation being divided into a plurality of slitshaped sections by means of spaced apart bridges extending across saidperforation in a direction perpendicular to said first mentioneddirection, a fluorescent screen including a plurality of stripe shapedphosphors corresponding to said stripe shaped perforations, and anelectron gun assembly, the improvement wherein the height of saidbridges is made approximately onehalf the thickness of said colourselecting member so that adjacent said slit shaped sections areseparated by said bridges on the side facing to said electron gunassembly whereas they merge with each other on the side facing to saidfluorescent screen to form said perforation as continuous stripe shapedopenings.

2. The colour picture tube according to claim 1 wherein said stripeshaped perforations extend in the direction of vertical deflection.

3. The colour picture tube according to claim 1 wherein said stripeshaped perforations extend in the direction of horizontal deflection.

4. The colour picture tube according to claim 1 wherein thecross-sectional area of each bridge decreases gradually from the sidethereof facing to said electron gun assembly toward said fluoroscentscreen.

5. The colour picture tube according to claim 1 wherein the height ofsaid bridges is larger than one half of the thickness of said colourselecting member.

6. The colour picture tube according to claim 1 wherein the height ofsaid bridges is substantially equal to one half of the thickness of saidcolour selecting member.

7. The colour picture tube according to claim 1 wherein the height ofsaid bridges is smaller than one half of the thickness of said colourselecting member.

8. The colour picture tube according to claim 1 wherein said bridges ofsaid stripe shaped perforations are aligned in said first mentioneddirection.

9. The colour picture tube according to claim 1 wherein said bridges ofsaid stripe shaped perforations are staggered in said first mentioneddirection.

10. The colour picture tube according to claim 1 wherein said bridgesprotrude slightly beyond the surface of said colour selecting member onthe side thereof facing to said electron gun assembly.

1. In a color picture tube comprising a colour selecting member providedwith a plurality of stripe shaped parallel perforations extending in adirection parallel to one side of the picture displayed by said tube,each stripe shaped perforation being divided into a plurality of slitshaped sections by means of spaced apart bridges extending across saidperforation in a direction perpendicular to said first mentioneddirection, a fluorescent screen including a plurality of stripe shapedphosphors corresponding to said stripe shaped perforations, and anelectron gun assembly, the improvement wherein the height of saidbridges is made approximately one-half the thickness of said colourselecting member so that adjacent said slit shaped sections areseparated by said bridges on the side facing to said electron gunassembly whereas they merge with each other on the side facing to saidfluorescent screen to form said perforation as continuous stripe shapedopenings.
 2. The colour picture tube according to claim 1 wherein saidstripe shaped perforations extend in the direction of verticaldeflection.
 3. The colour picture tube according to claim 1 wherein saidstripe shaped perforations extend in the direction of horizontaldeflection.
 4. The colour picture tube according to claim 1 wherein thecross-sectional area of each bridge decreases gradually from the sidethereof facing to said electron gun assembly toward said fluoroscentscreen.
 5. The colour picture tube according to claim 1 wherein theheight of saId bridges is larger than one half of the thickness of saidcolour selecting member.
 6. The colour picture tube according to claim 1wherein the height of said bridges is substantially equal to one half ofthe thickness of said colour selecting member.
 7. The colour picturetube according to claim 1 wherein the height of said bridges is smallerthan one half of the thickness of said colour selecting member.
 8. Thecolour picture tube according to claim 1 wherein said bridges of saidstripe shaped perforations are aligned in said first mentioneddirection.
 9. The colour picture tube according to claim 1 wherein saidbridges of said stripe shaped perforations are staggered in said firstmentioned direction.
 10. The colour picture tube according to claim 1wherein said bridges protrude slightly beyond the surface of said colourselecting member on the side thereof facing to said electron gunassembly.